1. Field of the Invention
The present invention relates to a ball bearing inspection apparatus for inspecting a ball bearing for surface defects of rolling elements (balls), or the like, interposed between inner and outer races of the ball bearing by detecting vibration generated when rotating the inner and outer races relatively to each other.
2. Description of the Related Art
In a ball bearing incorporated in a precision machine such as a hard disk driving device, or the like, there is a possibility that vibration may be caused by rotation even in the case where a surface of any one of races or balls has a little defect. Therefore, the ball bearing to be incorporated in such a precision machine must be individually inspected for defects of ball surfaces, or the like, by a ball bearing inspection apparatus.
As this type ball bearing inspection apparatus, there is known a conventional apparatus for inspecting a ball bearing for defects by detecting vibration (sound) caused by rotation when relatively rotating inner and outer races of the ball bearing to each other. For example, the conventional ball bearing inspection apparatus is formed so that an outer race is rotated by a rotation shaft in the condition that an inner race is fixed to a stationary shaft. On this occasion, the stationary shaft is pressed with a predetermined load in an axial direction by a cylinder. In this manner, the stationary shaft press the inner race to thereby apply a pre-load to balls. The magnitude of the pre-load is set to be equal to that in use of the ball bearing. In this condition, vibration (sound) caused by rotation is detected by a vibrometer (mircophone), and a judgment is made on the basis of a result of the detection as to whether any one of ball surfaces has a defect or not.
The aforementioned conventional ball bearing inspection apparatus is, however, able to inspect no area but a constant contact area (running trace) of ball surfaces because the balls are loaded with a predetermined constant load (pre-load) in the inspecting operation (even though there is a clearance in the ball bearing itself), so that there is no large change in balls' own rotation axes. There is a possibility that a large part of the ball surfaces except the range of the running trace is unable to be inspected.
On the other hand, changing the load to be applied in the axial direction might be thought of. The balls' own rotation axes are, however, unable to be changed greatly by such a simple means of changing the load. There is still a possibility that a lot of portions which have not been inspected yet might be left.
In addition, applying a pre-loading the balls in a reverse direction to change the balls' own rotation axes by inverting an installing posture of the ball bearing as an object into the ball bearing inspection apparatus might be thought of. Installing operation (that is, an operation in which the ball bearing is installed into the ball bearing inspection apparatus), however, has to be repeated by a plurality of times. There is an expected problem that a long time is required for the inspection.